#!/bin/bash

# Explicitly set the PATH to that of ENV_SUPATH in /etc/login.defs and unset
# various other variables. We need to do this so /sbin/dhclient cannot abuse
# the environment to escape AppArmor confinement via this script
# (LP: #1045986). This can be removed once AppArmor supports environment
# filtering (LP: #1045985)
export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export ENV=
export BASH_ENV=
export CDPATH=
export GLOBIGNORE=
export BASH_XTRACEFD=

# dhclient-script for Linux. Dan Halbert, March, 1997.
# Updated for Linux 2.[12] by Brian J. Murrell, January 1999.
# Modified for Debian.  Matt Zimmerman and Eloy Paris, December 2003
# Modified to remove useless tests for antiquated kernel versions that
# this doesn't even work with anyway, and introduces a dependency on /usr
# being mounted, which causes cosmetic errors on hosts that NFS mount /usr
# Andrew Pollock, February 2005
# Modified to work on point-to-point links. Andrew Pollock, June 2005
# Modified to support passing the parameters called with to the hooks. Andrew Pollock, November 2005

# The alias handling in here probably still sucks. -mdz

# log an error.
error() { logger -p daemon.err "$@"; }

# wait for given file to be writable
wait_for_rw() {
    local file=$1
    # Find out whether we are going to mount / rw
    exec 9>&0 </etc/fstab
    rootmode=rw
    while read dev mnt type opts dump pass junk; do
        [ "$mnt" != / ] && continue
        case "$opts" in
            ro|ro,*|*,ro|*,ro,*)
               rootmode=ro
               ;;
             esac
     done
     exec 0>&9 9>&-
 
    # Wait for $file to become writable
    if [ "$rootmode" = "rw" ]; then
        while ! { : >> "$file"; } 2>/dev/null; do
            sleep 0.1
        done
    fi
}

# update /etc/resolv.conf based on received values
make_resolv_conf() {
    local old_ns="" resolv_conf="" new_resolv_conf=""
    [ -e /etc/resolv.conf ] && old_ns=$(grep -i '^nameserver' /etc/resolv.conf)

    resolv_conf=$(readlink -f "/etc/resolv.conf" 2>/dev/null) ||
        resolv_conf="/etc/resolv.conf"

    # write to temp file in same directory as target
    new_resolv_conf="${resolv_conf}.dhclient-new.$$"

    # DHCPv4
    if [ -n "$new_domain_search" ] || [ -n "$new_domain_name" ] ||
       [ -n "$new_domain_name_servers" ]; then
        wait_for_rw "$new_resolv_conf"

        {
        if [ -n "$new_domain_name" ]; then
            echo domain ${new_domain_name%% *}
        fi

        if [ -n "$new_domain_search" ]; then
            if [ -n "$new_domain_name" ]; then
                domain_in_search_list=""
                for domain in $new_domain_search; do
                    if [ "$domain" = "${new_domain_name}" ] ||
                       [ "$domain" = "${new_domain_name}." ]; then
                        domain_in_search_list="Yes"
                    fi
                done
                if [ -z "$domain_in_search_list" ]; then
                    new_domain_search="$new_domain_name $new_domain_search"
                fi
            fi
            echo "search ${new_domain_search}"
        elif [ -n "$new_domain_name" ]; then
            echo "search ${new_domain_name}"
        fi

        if [ -n "$new_domain_name_servers" ]; then
            for nameserver in $new_domain_name_servers; do
                echo nameserver $nameserver
            done
        elif [ -n "$old_ns" ]; then # keep 'old' nameservers
            echo "$old_ns"
        fi
        } > "$new_resolv_conf"
    # DHCPv6
    elif [ -n "$new_dhcp6_domain_search" ] || [ -n "$new_dhcp6_name_servers" ]; then
        wait_for_rw "$new_resolv_conf"

        {
        if [ -n "$new_dhcp6_domain_search" ]; then
            echo "search ${new_dhcp6_domain_search}"
        fi

        if [ -n "$new_dhcp6_name_servers" ]; then
            for nameserver in $new_dhcp6_name_servers; do
                echo nameserver $nameserver
            done
        elif [ -n "$old_ns" ]; then # keep 'old' nameservers
            echo "$old_ns"
        fi
        } > "$new_resolv_conf"
    fi

    [ -e "$resolv_conf" ] &&
        chmod --reference="$resolv_conf" "$new_resolv_conf" &&
        chown --reference="$resolv_conf" "$new_resolv_conf"
    
    mv "$new_resolv_conf" "$resolv_conf" ||
        { rm -f "$new_resolv_conf"; return 1; }
}

# set the link up and wait for ipv6 link local dad to finish
ipv6_link_up_and_dad() {
    local dev=$1 delay=${2:-0.1} attempts=${3:-60}
    ip link set up dev "$dev" ||
        { error "$dev: failed to set link up"; return 1; }
    local n=0
    while :; do
        n=$((n+1))
        # note: busybox ip does not understand 'tentative' as input
        # so we cannot just use the tentative flag and check for empty
        out=$(ip -6 -o address show dev "$dev" scope link) || {
            error "$dev: checking for link-local addresses failed";
            return 1
        }
        case " $out " in
            *\ dadfailed\ *)
                error "$dev: ipv6 dad failed."
                return 1;;
            *\ tentative\ *) :;;
            *) return 0;;
        esac
        [ $n -lt $attempts ] || {
            error "$dev: time out waiting for permanent link-local address"
            return 1;
        }
        sleep $delay
    done
}

# run given script
run_hook() {
    local script
    local exit_status
    script="$1"
    shift	# discard the first argument, then the rest are the script's

    if [ -f $script ]; then
        . $script "$@"
    fi

    if [ -n "$exit_status" ] && [ "$exit_status" -ne 0 ]; then
        logger -p daemon.err "$script returned non-zero exit status $exit_status"
    fi

    return $exit_status
}

# run scripts in given directory
run_hookdir() {
    local dir
    local exit_status
    dir="$1"
    shift	# See run_hook

    if [ -d "$dir" ]; then
        for script in $(run-parts --list $dir); do
            run_hook $script "$@" || true
            exit_status=$?
        done
    fi

    return $exit_status
}

# Must be used on exit.   Invokes the local dhcp client exit hooks, if any.
exit_with_hooks() {
    exit_status=$1

    # Source the documented exit-hook script, if it exists
    if ! run_hook /etc/dhcp/dhclient-exit-hooks "$@"; then
        exit_status=$?
    fi

    # Now run scripts in the Debian-specific directory.
    if ! run_hookdir /etc/dhcp/dhclient-exit-hooks.d "$@"; then
        exit_status=$?
    fi

    exit $exit_status
}


# set up some variables for DHCPv4 handlers below
if [ -n "$new_broadcast_address" ]; then
    new_broadcast_arg="broadcast $new_broadcast_address"
fi
if [ -n "$old_broadcast_address" ]; then
    old_broadcast_arg="broadcast $old_broadcast_address"
fi
if [ -n "$new_subnet_mask" ]; then
    new_mask="/$new_subnet_mask"
fi
if [ -n "$alias_subnet_mask" ]; then
    alias_mask="/$alias_subnet_mask"
fi
# The 576 MTU is only used for X.25 and dialup connections
# where the admin wants low latency.  Such a low MTU can cause
# problems with UDP traffic, among other things.  As such,
# disallow MTUs from 576 and below by default, so that broken
# MTUs are ignored, but higher stuff is allowed (1492, 1500, etc).
if [ -z "$new_interface_mtu" ] || [ "$new_interface_mtu" -lt 576 ]; then
    new_interface_mtu=''
fi
if [ -n "$IF_METRIC" ]; then
    metric_arg="metric $IF_METRIC"	# interfaces(5), "metric" option
fi


# The action starts here

# Invoke the local dhcp client enter hooks, if they exist.
run_hook /etc/dhcp/dhclient-enter-hooks
run_hookdir /etc/dhcp/dhclient-enter-hooks.d

# Execute the operation
case "$reason" in

    ### DHCPv4 Handlers

    MEDIUM|ARPCHECK|ARPSEND)
        # Do nothing
        ;;
    PREINIT)
        # The DHCP client is requesting that an interface be
        # configured as required in order to send packets prior to
        # receiving an actual address. - dhclient-script(8)

        # ensure interface is up
        ip link set dev ${interface} up

        if [ -n "$alias_ip_address" ]; then
            # flush alias IP from interface
            ip -4 addr flush dev ${interface} label ${interface}:0
        fi

        ;;
    BOUND|RENEW|REBIND|REBOOT)
        if [ -n "$old_host_name" ] && [ ! -s /etc/hostname ]; then
            # hostname changed => set it
            hostname "$new_host_name"
        fi

        if [ -n "$old_ip_address" ] && [ -n "$alias_ip_address" ] &&
           [ "$alias_ip_address" != "$old_ip_address" ]; then
            # alias IP may have changed => flush it
            ip -4 addr flush dev ${interface} label ${interface}:0
        fi

        if [ -n "$old_ip_address" ] &&
           [ "$old_ip_address" != "$new_ip_address" ]; then
            # leased IP has changed => flush it
            ip -4 addr flush dev ${interface} label ${interface}
        fi

        if [ -z "$old_ip_address" ] ||
           [ "$old_ip_address" != "$new_ip_address" ] ||
           [ "$reason" = "BOUND" ] || [ "$reason" = "REBOOT" ]; then
            # new IP has been leased or leased IP changed => set it
            ip -4 addr add ${new_ip_address}${new_mask} ${new_broadcast_arg} \
                dev ${interface} label ${interface}

            if [ -n "$new_interface_mtu" ]; then
                # set MTU
                ip link set dev ${interface} mtu ${new_interface_mtu}
            fi

            for router in $new_routers; do
                if [ "$new_subnet_mask" = "255.255.255.255" ]; then
                    # point-to-point connection => set explicit route
                    ip -4 route add ${router} dev $interface >/dev/null 2>&1
                fi

                # set default route
                ip -4 route add default via ${router} dev ${interface} \
                    ${metric_arg} >/dev/null 2>&1
            done
        fi

        if [ -n "$alias_ip_address" ] &&
           [ "$new_ip_address" != "$alias_ip_address" ]; then
            # separate alias IP given, which may have changed
            # => flush it, set it & add host route to it
            ip -4 addr flush dev ${interface} label ${interface}:0
            ip -4 addr add ${alias_ip_address}${alias_mask} \
                dev ${interface} label ${interface}:0
            ip -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1
        fi

        # update /etc/resolv.conf
        make_resolv_conf

        ;;

    EXPIRE|FAIL|RELEASE|STOP)
        if [ -n "$alias_ip_address" ]; then
            # flush alias IP
            ip -4 addr flush dev ${interface} label ${interface}:0
        fi

        if [ -n "$old_ip_address" ]; then
            # flush leased IP
            ip -4 addr flush dev ${interface} label ${interface}
        fi

        if [ -n "$alias_ip_address" ]; then
            # alias IP given => set it & add host route to it
            ip -4 addr add ${alias_ip_address}${alias_network_arg} \
                dev ${interface} label ${interface}:0
            ip -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1
        fi

        ;;

    TIMEOUT)
        if [ -n "$alias_ip_address" ]; then
            # flush alias IP
            ip -4 addr flush dev ${interface} label ${interface}:0
        fi

        # set IP from recorded lease
        ip -4 addr add ${new_ip_address}${new_mask} ${new_broadcast_arg} \
            dev ${interface} label ${interface}

        if [ -n "$new_interface_mtu" ]; then
            # set MTU
            ip link set dev ${interface} mtu ${new_interface_mtu}
        fi

        # if there is no router recorded in the lease or the 1st router answers pings
        if [ -z "$new_routers" ] || ping -q -c 1 "${new_routers%% *}"; then
            if [ -n "$alias_ip_address" ] &&
               [ "$new_ip_address" != "$alias_ip_address" ]; then
                # separate alias IP given => set up the alias IP & add host route to it
                ip -4 addr add ${alias_ip_address}${alias_mask} \
                    dev ${interface} label ${interface}:0
                ip -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1
            fi

            # set default route
            for router in $new_routers; do
                ip -4 route add default via ${router} dev ${interface} \
                    ${metric_arg} >/dev/null 2>&1
            done

            # update /etc/resolv.conf
            make_resolv_conf
        else
            # flush all IPs from interface
            ip -4 addr flush dev ${interface}
            exit_with_hooks 2 "$@"
        fi

        ;;

    ### DHCPv6 Handlers
    # TODO handle prefix change: ?based on ${old_ip6_prefix} and ${new_ip6_prefix}?

    PREINIT6)
        # ensure interface is up
        ipv6_link_up_and_dad "$interface"

        # flush any stale global permanent IPs from interface
        ip -6 addr flush dev ${interface} scope global permanent

        ;;

    BOUND6|RENEW6|REBIND6)
        if [ "${new_ip6_address}" ]; then
            # set leased IP
            ip -6 addr add ${new_ip6_address} \
                dev ${interface} scope global
        fi

        # update /etc/resolv.conf
        if [ "${reason}" = BOUND6 ] ||
           [ "${new_dhcp6_name_servers}" != "${old_dhcp6_name_servers}" ] ||
           [ "${new_dhcp6_domain_search}" != "${old_dhcp6_domain_search}" ]; then
            make_resolv_conf
        fi

        ;;

    DEPREF6)
        # set preferred lifetime of leased IP to 0
        ip -6 addr change ${cur_ip6_address} \
            dev ${interface} scope global preferred_lft 0

        ;;

    EXPIRE6|RELEASE6|STOP6)
        if [ -z "${old_ip6_address}" ]; then
            exit_with_hooks 2
        fi

        # delete leased IP
        ip -6 addr del ${old_ip6_address} \
            dev ${interface}

        ;;
esac

exit_with_hooks 0